Several indirect lines of evidence suggest that sexual transmission plays a major role in the epidemiology of cytomegalovirus (CMV) infection in adolescents and young adults. Sexual transmission of CMV presumably can result in subclinical infection and in clinically apparent primary infection, and may result in reinfection and cogential infection as well. The principal goal of this project is to examine the epidemiology, clinical manifestations, and natural history of CMV infection in sexually active persons. Using both prevalence surveys and cohort studies, we will systematically analyze and correlate clinical manifestations, antibody to CMV, and viral shedding on the one hand, with sexual practices, levels of sexual activity, changes in sex partners, and other correlates of sexual activity on the other. Populations to be studied include clients of sexually transmitted disease (STD) clinics and university student health clinics; sex partners of persons with and without CMV infection; and sexually active persons with clinical syndromes suspected to be related to CMV infection. Restriction enzyme typing will be used to assess sexual transmission by comparing isolates from sex partners and to distinguish endogenous relapse from exogenous reinfection in longitudinally followed cohorts. Antigen detection techniques (e.g., enzyme-linked fluorescent antibody) will be developed and compared with viral isolation to detect shedding of CMV and to assess infectivity of semen and endocervical secretions.